1. Field of the Invention
The present invention relates to a filament for an infrared lamp used as a heater, such as a dry chamber for industry and a method of manufacturing the same, and more particularly, to a filament for an infrared lamp having excellent infrared radiation efficiency, electrical performance, and durability using a thin graphite plate and a method of manufacturing the same.
2. Background of the Related Art
An infrared lamp operated by a common power source is being widely used as heating apparatuses, such as a dry chamber for industry, a heater for home use, and a cooker. FIG. 1 is an exemplary diagram of a conventional infrared lamp.
As shown, an internal lead wire 3 on both ends of a filament 2 is connected to relay pieces 4 formed of a thin metal plate. Next, the other ends of the relay pieces 4 are connected to external lead wires 5. Furthermore, the filament 2 is inserted into a transparent quartz tube 1 into which an inert gas is injected. Both ends of the quartz tube 1 are pinch-sealed. When a power source is supplied to the external lead wires 5, infrared rays are radiated in all directions from the filament 2 within the quartz tube 1.
The filament of the infrared lamp is chiefly made of carbon. The carbon-material filament includes several types, such as a carbon sponge filament of a bar shape, a carbon sintering filament of a strip shape, and a spiral carbon strip filament formed by twisting several strings of carbon threads to form a strip shape and then forming the strip shape into a spiral shape.
Meanwhile, the conventional filament made of carbon has the following problems. First, the bar-shaped carbon sponge filament is problematic in that it is very difficult to meet a desired resistance value according to the resistance characteristic of carbon itself and that infrared rays are not uniformly radiated because the density of the sponge is not uniform and thus current does not flow into some portions of the sponge. Further, the bar-shaped carbon sponge filament is problematic in that the lifespan is short because of a difference in the temperature between the surface and the central portion of the filament because it has the bar shape.
In the strip-shaped carbon sintering filament, the filament is stretched when light is emitted, and curve or deformation is generated because of a thin and wide width. Furthermore, if the width is 10 mm or more, there are problems in that a plastic task is difficult and strength is weak. If the length is 500 mm or more, there is a problem in that the filament is difficult to fabricate. For the above reasons, a long lamp is fabricated by connecting two or more short filaments using a middle medium. However, the long lamp is problematic in that the filament is likely to be broken, a special adhesive for adhering the middle medium to the filament has to be used, and the radiation of infrared rays is not uniform because the middle medium does not emit light.
In the spiral carbon strip filament, when light is emitted, the length of the filament is stretched and the filament is bent. Consequently, the filament reaches the wall of the quartz tube, thereby contaminating the quartz tube. In worse cases, the quartz tube is damaged. Furthermore, the inside of the filament is hollowed out, and a gap is formed between the filaments. Accordingly, since concentrated energy is not efficiently used, the surface area of the filament versus emission efficiency is low and thus power consumption is high.
Furthermore, if the length of the filament is increased, pressurization is irregular when molding is performed, and deformation is likely to occur when plasticity is performed. Further, if the gap between the filaments is not regular, temperature differs according to the location of the filament and thus energy efficiency is low. Moreover, since it is difficult to place the filament at the internal center of the quartz tube, an elaborate and experienced task is required, thereby making it difficult to increase productivity.
As described above, the conventional carbon-material filament is problematic in that the radiation efficiency of infrared rays is low, radiation is not regular, power consumption is great, the lifespan is short, manufacture is difficult, and productivity is low.